Leslie West used them too with modifications. From Wikipedia:I had no idea Sunn Amplifiers were making a return. I remember being able to buy Sunns for cheap in the 80s and 90s.
"The Sunn amplifiers that West used were of the late 1960s era and were not factory stock. The 4-channel amplifier heads' preamps were wired as cascading preamps to 1 channel, out to the amp's power section. That's what produced the long compressed sustain and distorted overdrive of the great Mountain sound that he is well known for. This is years before Mesa Boogie Amplifiers with a similar idea got their amps on the world stage, but Boogies do have their own sound comparatively."